Theresa May has told her NATO allies that the lesson of the Manchester bomb attack is that the alliance must spend more on arms to raise its game against “terrorism.” Her comment exposes the Prime Minister’s inability to examine the causes of jihadist extremism or to critically assess imperialism’s record of collaboration with it.

Allowing home-grown jihadists to go to Libya to overthrow the Muammar Gaddafi regime while providing them with air support, as Britain and France did, might have seemed clever at the time.

It secured the removal of an inconvenient leader who had metamorphosed from terrorism sponsor to valuable trading partner – remember Tony Blair’s “tent-in-the-desert” reconciliation with Gaddafi – and back to outcast status.

But Gadaffi’s removal had unforeseen consequences – not least fragmentation of the Libyan state, its supplanting by clan-based regional warlords and an opportunity for Islamic State (ISIS) to fish in troubled waters.

That chaotic outcome was foreseen by [Labour Party leader] Jeremy Corbyn, John McDonnell and just 11 other MPs in the House of Commons.

The rest were carried along by the “we’ve got to do something” brigade, which translates almost always into military meddling, supplying arms or unleashing the RAF to bomb one side or the other.

Assisting regime change in Libya followed just eight years after Blair’s dodgy dossier and a media tsunami of pro-war propaganda convinced MPs and those desperate to be persuaded that invading Iraq was a sound idea.

The result: a dysfunctional state, sectarian government, political priorities guided by national or religious affiliation and the birth of Islamic State powered by the arms and demobilised troops of the defeated Iraqi army.

Corbyn called this one right too, unlike those Labour backbenchers who deride his leadership qualities and, of course, our “strong and stable” Prime Minister.

Before Iraq was Afghanistan when Ronald Reagan’s US administration authorised supplies of sophisticated weaponry, including surface-to-air missiles, to the so-called mojahedin, including one Osama bin Laden, who had risen up against a progressive government backed by the Soviet Union.

Their seizure of power was succeeded by a carnival of corruption and chaos, following which the Taliban, armed and trained by Pakistani intelligence services, drove out the warlords only for the US and Britain to return them to power in 2001 after the Twin Towers atrocity carried out by a largely Saudi Arabian conspiracy.

When campaigning for the US presidency, Donald Trump said: “Who blew up the World Trade Centre? It wasn’t the Iraqis, it was Saudi – take a look at Saudi Arabia, open the documents.”

Last week, he signed a US$110 billion arms deal with the Riyadh autocracy, backing its horrific slaughter of civilians in Yemen.

Neither he nor May, who also sells arms to the House of Saud, is unaware that this is the source of Wahhabism, the extreme interpretation of Islam adopted by jihadists who have declared war on the 21st century and been armed by Saudi Arabia and its allies.

Yet the US and Britain choose to ride the Saudi tiger, supporting its bloody rampage in Syria while being shocked by outrages such as Manchester when European targets are hit.

Ramping up an arms race in response to Manchester is both wrong and futile.

It makes more sense to rethink foreign policy, help to end wars in the Middle East and work through the United Nations to help the millions of civilians ravaged by wars.